Bryophytes of the Chaco
Chaco forest.. Photograph by A. Fuentes.
The Chaco, or Gran Chaco, is located in the lowlands of southeast Bolivia, bordered on the west by the subandian Chaco Serrano, in the north by Chiquitano forest, and to the east by the Pantanal. Chaco vegetation extends into northwest Paraguay and northern Argentina. Approximately 10% (105,006 km2) of the land surface of Bolivia is comprised of Chaco forest. This vegetation type is found in the Bolivian departments of Santa Cruz, Chuquisaca and Tarija. Elevation ranges from 200 to 600 meters. The annual average temperatures range from 25-26º C, with a maximum of 48º C, and minimum of 1º C due to the southerly winds (surazos). Annual average precipitation ranges from 400-900 mm (to 1000 mm adjoining the Pantanal and the Chaco Serrano), with approximately 6-10 dry months.
Map of the Chaco. Cortesía de FAN (Fundación Amigos de la Naturaleza), Santa Cruz de la Sierra, Bolivia.
The vegetation, the driest lowland ecoregion in Bolivia, is characterized by open or closed low deciduous dry forest. The region is characterized topographically by plains and hills or low mountains (cerrado). Vascular plant diversity is presently unknown, but less than the Amazon or Chiquitano. Important vascular plant families include: Anacardiaceae, Apocynaceae, Capparidaceae, Leguminosae and Rhamnaceae. Tree diversity is 50-100 species. Important tree species include: Aspidosperma quabracho-blano, Chorisia insignis, Cereus dayamii, Geoffrea decorticans, Ruprechita triflora, Schinopsis quebracho-colorado, Stetsonia coryne, Trithrinax schizophylla, and Zizphus mistol. Epiphyte diversity is estimated at less than 50 species represented mainly by the Bromeliaceae and Orchidaceae. A high level of endemism is represented in the Chaco, although the exact number of species is unknown.
The Chaco is likely the least diverse ecoregion in Bolivia for bryophytes. How many bryophytes are present in the Chaco ecoregion awaits further analysis. At present only 19 species are listed. There may be about 20-30 species of hepatics, and for mosses about 50-70 species. Mosses are represented by a few species of the Bryaceae, Fissidentaceae, Pottiaceae, and Stereophyllaceae; Fissidens may provide to be the most diverse genus (which is true of Paraguayan Chaco, unpublished data). There are few leafy hepatics, possibly the most diverse genus may be represented by Frullania. There may be, however, a rather significant number of thalloid hepatics, particularly the genus Riccia that have yet to be recorded for Bolivia but found in adjoining regions of Brazil, Paraguay, and Argentina. An optimal time for collecting thalloid hepatics in the Chaco will likely be shortly following the rainy season (even by 4-wheel vehicle in the rainy season is nearly impossible), or along seasonally wet stream banks or lake and pond margins.
Hepatics: Frullania ericoides. Mosses: Entodontopsis leucostega, Erpodium beccarii, Erpodium coronatum, Fabronia ciliaris var. polycarpa, Stereophyllum radiculosum, Syntrichia chisosa, Tortella humilis.
Mosses: Entodon micans, Entodontopsis leucostega, Fabronia ciliaris, Haplocladium microphyllum, Schlotheimia rugifolia, Stereophyllum radiculosum, Tortella humilis.
Soil (and soil covered rocks).
Hepatics: Cronisia fimbriata, Frullania ericoides. Mosses: Bryum argenteum, Bryum capillare, Entodon micans, Fissidens goyazensis, Fissidens zollingeri, Gertrudiella validinervis, Hyophila involuta, Lorentziella imbricata, Syntrichia xerophila.
Navarro, G. 2004. Mapa de Vegetación del Parque Nacional y Area Natural de Manejo Integrado “Kaa-Iya.” Editorial FAN, Santa Cruz.
Prado, D.E. 1993. What is the Gran Chaco vegetation in South America. I. A review: contribution to the study of flora and vegetation of the Chaco. Candollea 48: 145-172.
Spichiger, R. & L. Ramella. 1989. The forests of the Paraguayan Chaco. Pages 259-270, In: L.B. Holm-Nielsen, L.C. Christensen & H. Balslev (eds.). Tropical Forests: Botanical Dynamics, Speciation and Diversity. Academic Press, London.
Bryophyte Checklist of the Chaco Region
Cronisia fimbriata (Nees) Whittem. & Bischl. [new to Bolivia]
Frullania ericoides (Nees ex Mart.) Mont.
Bryum argenteum Hedw.
Bryum capillare Hedw.
Erpodium coronatum (Hook. f. & Wilson) Mitt.
Fabronia ciliaris var. polycarpa (Hook.) W.R. Buck
Fissidens goyazensis Broth.
Fissidens pallidinervis Mitt. [syn. F. minutus Thwaites & Mitt.]
Fissidens zollingeri Mont.
Lorentziella imbricata (Mitt.) Broth.
Haplocladium microphyllum (Hedw.) Broth.
Schlotheimia rugifolia (Hook.) Schwägr.
Gertrudiella validinervis (Herzog) Broth. [rare, marginal]
Hyophila involuta (Hook.) A. Jaeger
Syntrichia chisosa (Magill, Delgad. & L. R. Stark) R.H. Zander
Syntrichia xerophila (Herzog) S.P. Churchill [= Pseudocrossidium; rare?, marginal]
Tortella humilis (Hedw.) Jenn.
Entodontopsis leucostega (Brid.) W.R. Buck & Ireland
Stereophyllum radiculosum (Hook.) Mitt.